This invention relates generally to threaded nuts adapted to lock onto bolts and, more particularly, to lock nuts that resiliently deform when bolts are threaded into them.
Lock nuts of this particular kind are disclosed in U.S. Pat. No. 4,805,288, entitled "Method For Making and Using a Locking Beam Nut." That patent discloses one-piece lock nuts of the kind that include a generally rigid body with a threaded opening extending through it and with a plurality of resilient, circumferentially-spaced locking beams projecting from one end of the rigid body. Inner surfaces of the locking beams define a threaded opening aligned with the threaded opening of the rigid body. The locking beams, which are integral with the rigid body, deviate radially inwardly such that the threaded opening they define has a uniformly-decreasing diameter When a bolt is threaded into the nut, the locking beams resiliently flex radially outwardly, to frictionally lock the bolt in place. The locking beams are separated from each other by narrow, uniform slots, and the confronting side walls of adjacent beams, which define each slot, diverge from each other with increasing radial distance. The amount of divergence is uniform along the lengths of the beams.
Lock nuts of this kind are frequently used in environments where debris can become encrusted in the narrow slots between the locking beams. The divergent side wall configuration for the slots ensures that this rigid debris will not prevent the flexed beams from returning to their unflexed, radially-inward positions when the bolt is removed. This is an important feature that enables the lock nut to be subsequently reused with substantially the same locking qualities, yet without requiring a special cleaning of the slots.
The lock nut described briefly above has proven to function generally satisfactorily in most situations. However, it is believed that the beam flexing can sometimes exceed the beams' elastic limits, such that when the bolt is removed, the beams do not return fully to their original, radially-inward positions. Consequently, when the lock nut is again used to threadedly receive a bolt, especially a bolt having a slightly smaller diameter than the first bolt, the lock nut might not grip the bolt with the desired compressive force. Another drawback to the lock nut described above is that the divergence of the confronting side walls defining each of the narrow slots can reduce the size of each beam so much that it no longer has the desired strength. Failures can therefore sometimes occur at the base of each beam.
Another form of lock nut includes the same kind of rigid body as described above, but with a generally cylindrical sleeve projecting from one end of the body and having a threaded opening that is deformed into an oval shape. The oval's minor transverse dimension is slightly less than the diameter of the threaded opening in the rigid body, and the oval's major transverse dimension is slightly greater than that diameter. When a bolt is threaded into the lock nut, the narrow sides of the oval flex outwardly, to frictionally lock the bolt in place. Lock nuts of this kind, which are sometimes called shank nuts, are available from Kaynar Microdot and Bristol Industries.
Although this latter kind of lock nut functions generally satisfactorily in most situations, the flexing of the oval sleeve occurs principally only at the base of the sleeve and can exceed the sleeve's elastic limit. Consequently, when the lock nut is subsequently reused with another bolt, especially a bolt having a slightly smaller diameter than the first bolt, the lock nut might not grip the bolt with the desired compressive force.
It should, therefore, be appreciated that there is a need for an improved lock nut that can be used repeatedly to lock onto many different bolts without any significant reduction in gripping force. It should also be appreciated that there is a need for a lock nut of the kind that includes a plurality of locking beams where the nut functions well in the presence of rigid debris encrusted in the narrow slots between the beams, without unduly compromising beam strength The present invention fulfills these needs.